Modified Joint and Corset Prosthesis Designs

One of the aspects of my consulting practice that I find most enjoyable is the chance to see the clever ways colleagues across the country have solved clinical problems. In my travels to various locations in the upper Midwest this spring, I noted several examples of applying the principles of the old-fashioned leather corset and side joint prostheses to solve contemporary clinical problems. Although I cannot cite a written reference, several people have ascribed the basic concepts illustrated here to Carl Caspers, CPO, a well-respected clinician who formerly practiced in the St. Cloud, Minnesota area and often shared his ideas with area colleagues.

The universal indications for joint and corset limbs have been:

  1. Unloading a damaged residual limb
  2. Stabilizing an unstable knee
  3. Increasing mediolateral stability for a short residual limb

These benefits must be weighed against the limitations of the traditional molded leather corset and steel side joints, which include:

  1. Significant added weight and bulk
  2. Hygienic concerns with perspiration-stained leather
  3. The hassle of lacing the thigh corset

In recent decades, the use of traditional leather corset and side joint prostheses has become increasingly uncommon, being limited primarily to satisfied previous wearers who prefer the familiar "old timey" style of prosthesis that has served them well. I can't remember the last time I recommended the addition of a leather thigh corset to a prosthesis because the limitations of this material makes this approach objectionable to almost all new patients.

But, after my travels this year, I have revised my attitude toward the use of side joints. The examples depicted here mitigate many of the limitations of the traditional approach by using modern materials that are lighter, sleeker, more durable, more hygienic, and easier for patients to manage. I have now seen a number of clinical examples where such "modified joint and corset" designs have substantially improved the gait and stability for selected patients, including octogenarians, and have been well accepted and preferred by the amputees themselves.

The first example is from Bob Tillges, CPO's practice in Maplewood, Minnesota. The client is a lady who is approaching 90 years of age and has been a successful limited community ambulator using a walker for balance. Unfortunately, she has a residual limb with extremely soft tissue density that makes it physically impossible for her to obtain sufficient mediolateral stability with a corset-less prostheses; an extended trial with a supracondlar/suprapatellar prosthesis was not successful in increasing her stability while ambulating. She also has difficulty when arising from a chair, since her skeletal remnants are essentially unconstrained within the soft tissue envelope due to poor muscle tone.


This modified thigh corset provides excellent mediolateral stability using a lightweight anterior shell that has been laminated over a mold of the patient's thigh. It can be donned in a seated position with a single hook-and-loop strap and has proven suitable for patients of all ages, including geriatrics.
This modified thigh corset provides excellent mediolateral stability using a lightweight anterior shell that has been laminated over a mold of the patient's thigh. It can be donned in a seated position with a single hook-and-loop strap and has proven suitable for patients of all ages, including geriatrics.


This patient had a badly damaged residual limb and required a custom gel liner. The roll-on sleeve suspends the limb-liner combination in the socket, minimizing potentially destructive pistoning. The shuttle pin protruding from the socket allows the patient to don the prosthesis and custom corset from a seated position, and the shuttle lock anchors the socket to the rest of the prosthesis.
This patient had a badly damaged residual limb and required a custom gel liner. The roll-on sleeve suspends the limb-liner combination in the socket, minimizing potentially destructive pistoning. The shuttle pin protruding from the socket allows the patient to don the prosthesis and custom corset from a seated position, and the shuttle lock anchors the socket to the rest of the prosthesis.


Her current artificial limb includes a roll-on locking liner that she finds this easy to don from a seated position. The artificial limb is also donned from a seated position, with her knee flexed 90 degrees. Once the pin has engaged the shuttle lock, the patient swings the anterior shell down against the anterior surface of the thigh and fastens a single encircling hook-and-loop strap to secure it.

She reports that it is "a piece of cake" to put on the prosthesis since everything can be done while sitting. The proximal band, in combination with the sidebars, provides ample mediolateral stability and significantly reduces the loading on her residual limb during ambulation. This increases both comfort and stability, enabling her to walk as far as she is physically able to, with confidence.

The second example is a somewhat more complicated case where a custom-molded gel liner was required due to severe scarring on the residual limb, which is also quite short. In this configuration, the patient first dons the gel liner and then the socket, rolling up a knee sleeve to suspend both on the residual limb. A suspension pin, protruding from the end of the socket, engages a shuttle lock thus suspending the prosthesis. As before, the patient then swings the anterior band and sidebars down in contact with the thigh and closes a single hook-and-loop strap.

The final example is from Mike Gozola, CP's practice in Rochester, Minnesota that has been used successfully for many years by a young mother and teacher whose residual limb that was severely damaged by the trauma that led to the original amputation. Not only is her skin very fragile due to extensive scarring but her comminuted femoral fractures healed with a valgus angulation that puts tremendous stresses on the knee joint when she walks.


Posterior view of a custom molded thermoplastic thigh corset illustrating the posterior opening to facilitate donning while seated.
Posterior view of a custom molded thermoplastic thigh corset illustrating the posterior opening to facilitate donning while seated.


Thermoplastic corset and polycentric joints stabilize the knee and partially unload the residual limb, while the thin roll-on locking liner suspends the prosthesis without requiring a waist belt. The polyethylene foam insert is lighter and more durable than an equivalent thickness of gel and facilitates adjustments to the socket over time.
Thermoplastic corset and polycentric joints stabilize the knee and partially unload the residual limb, while the thin roll-on locking liner suspends the prosthesis without requiring a waist belt. The polyethylene foam insert is lighter and more durable than an equivalent thickness of gel and facilitates adjustments to the socket over time.


Off-the-shelf elastic knee support from the local discount pharmacy softens the contours of the prosthesis under clothing and protects clothing from the steel polycentric knee joints.
Off-the-shelf elastic knee support from the local discount pharmacy softens the contours of the prosthesis under clothing and protects clothing from the steel polycentric knee joints.

Biomechanically, she has all the indications for a classic joint and corset prosthesis. But, she also wants her prosthesis to be light, hygienic, easy to apply, and inconspicuous under slacks or longer skirts. Mike has used a custom molded thermoplastic thigh shell that encompasses the medial, anterior, and lateral surfaces of her thigh to provide the protection, stabilization, and unloading required.

A three millimeter roll-on silicone liner with shuttle lock provides both suspension and shear reduction. A removable polyethylene foam insert applied over the liner offers added skin protection and facilitates ongoing socket adjustments while being much lighter and more durable than the equivalent thickness of gel cushion liner.

To protect her clothing as well as to soften the contours of the prosthesis, this patient applies an off-the-shelf elastic knee support over the polycentric knee joints, extending from the proximal socket to the distal thigh section. She buys the knee supports at the local discount pharmacy, and replaces them every few months as they fray and lose their elasticity.



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